Method of and apparatus for sterilizing articles



K. A. o. WALLDEN 3,456,487

June 17, 1969 7 METHOD OF AND APPARATUS FOR STERQILIZING ARTICLESOriginal Filed Nov. -18, 1963 Sheet June-17, 1969 K. A. WALLDEN METHODOF AND APPARATUS FOR STERILIZING ARTICLES o'rigihal Filed Nov. 18, 1963Sheet 2 0:2

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lllll lllllllll .llllllllllllll United States Patent US. CI. 21-56 8Claims ABSTRACT OF THE DISCLOSURE An autoclave having a housing providedwith a top compartment overlying a chamber for sterilizing articles anda bottom compartment disposed about the chamber for holding a body ofwater heated to generate saturated steam passing into the topcompartment, flowing the saturated steam in the top compartment throughan elongated hollow member which is electrically heated to dry thesteam, discharging the dry steam from an apertured diffuser tube in theupper part of the sterilizing chamber, controlling the flow of the drysteam from the elongated member to the diffuser tube b a valve which isin the top compartment and has a control member accessible outside thehousing, heating the dry steam in the diffuser tube by saturated steamflowing from the bottom compartment to the top compartment through aconduit which extends through the diffuser tube, producing a firstpressure less than atmospheric pressure in the steam spaces of the topand bottom compartments of the housing by a first evacuator, andwithdrawing air and steam from the bottom part of the sterilizingchamber by a second evacuator to produce a second pressure therein whichis less than the first pressure.

This application is a continuation of application Ser. No. 325,807,filed Nov. 18, 1963, now abandoned.

As known it is necessary in hospitals to disinfect bedding and theclothes of certain patients. This can be performed in formalin chambersand also in autoclaves operated by saturated steam. Formalin chambers donot give an absolutely trustworthy result. Further, it is verytime-wasting to get rid of the objectionable odor of the disinfectedobjects. The autoclaves operated by saturated steam have a steamtemperature varying between 103 C. and 120 C. Due to the fact that wetsteam is used, it has turned out to be very diflicult and sometimesimpossible to dry bulky objects like mattresses, for example. It is thehumidity that spoils textile fabrics and not the rather high temperatureproduced during disinfection. Shoes and other leather products arecompletely destroyed at a temperature above 100 C. and hence in thedisinfection of such products the temperature should not exceed 80 C.They will then keep their form and softness.

The purpose of the present invention is to overcome these drawbacks. Themain feature of the invention is that saturated steam is produced in thelower compartment of a two-compartment container, housing a disinfectionchamber, at a pressure lower than atmospheric pressure, and the steam isdried in the upper compartment ofthe container by being fed throughtubes which are heated, and thereupon is distributed through a heateddiffuser tube in the upper portion of the disinfection chamber andfinally is withdrawn or sucked out from the lower portion of thedisinfection chamber. By means of this method it is possible to producea stream of dried steam with a temperature of about -80 C. through thedisinfection chamber. At this rather low temperature, which neverthelessis sufiiciently high to disinfect the objects in question, leatherproducts are not influenced in such a way that they are distorted andshoes which are disinfected in this manner retain their form. The steamfed to the disinfection chamber does not humidify the objects more thanit will be possible to dry them completely by a subsequent evacuation.

The invention also relates to an autoclave for carrying out the methodaccording to the invention. The autoclave comprises a disinfectionchamber housed in the lower compartment of a two-compartment containerand in provided with a diffuser tube for the steam. The autoclave ischaracterized by heating means for producing saturated steam in thelower compartment of the container at a pressure below the atmosphericpressure, by heating means for drying the steam before it reaches thediffuser tube, and by pump means for producing the lower pressure thanthe pressure of the steam in the disinfection chamber. In such anautoclave the heat losses will be very small and the condensation in theconduits to the disinfection chamber are practically completely avoided.

The invention will now be described with reference to the accompanying,partly diagrammatical drawings. In the drawings:

FIG. 1 is a vertical sectional view of an autoclave embodying theinvention,

FIG. 2 shows a horizontal section through the upper poiltion of theautoclave on the line IIII in FIG. 1, an

FIG. 3 shows a horizontal section on the line III-III in FIG. 1.

The autoclave shown in the drawings is adapted to produce the steamrequired for the disinfection. The autoclave comprises a container 3within which is provided a disinfection chamber 2, having a door 1. Thechamber 2 in partly surrounded by a body of water 4. The water level isindicated by a gauge glass 5. A horizontal partition 6 divides thecontainer 3 into a lower compartment 7, in which the body of water 4 isheld and an upper compartment 8 which functions as a steam chamber, Theupper compartment 8 communicates with the lower compartment 7 through aplurality of ports 9. A number of heating elements 11 in the lowercompartment 7 are controlled by thermostats 10, the heating elements 11being connected to a source of electric current (not shown). In thesteam chamber 8 a number of tubes 12, 13, 14 are connected in series.The tube 12 at one end 15 is in communication with the steam chamber orcompartment 8 and one end of the tube 14 is connected by a conduit 14ato a main valve 16 having its lower end connected to a diffuser tube 17provided in the upper part of the disinfection chamber 2. In each of thetubes 12, 13 and 14 is axially arranged an electric heating element 18.The electric current fed to the heating elements is controlled by asuitable automatic device (not shown). Such automatic device controlsthe whole disinfection process. The diffuser tube 17 may be providedwith a plurality of openings 19 or diffuser jets 20 or both. A conduit21 extends axially through the diffuser tube to one end of which isconnected a vertical tube 22 in communication with the upper.compartment or steam chamber 8 and the opposite end 23 of which is incommunication with the lower compartment 7 above the Water surface leveltherein.

A tube 25 extends downward from the bottom 24 of the disinfectionchamber 2 and has its lower end connected to a valve 26 which in turn isconnected to a vacuum pump 27. To the steam chamber or upper compartment8 is connected one end of a tube 28, the opposite end of which isconnected to a valve 29 which in turn is connected to a vacuum pump 30.

The method of disinfection is as follows: Electric current is suppliedto the heating elements 11. The vacuum pump 30 is started. When thepressure in the steam chamber or upper compartment 8 has been reduced toabout 410 mm. Hg, the pump 30 is stopped. At this pressure the steamtemperature in the upper compartment 8 is about 80 C. The objects to bedisinfected are now placed in the chamber 2. The door 1 is closed andthe vacuum pump 27 is started. The pressure in chamber 2 is reduced to avalue somewhat lower than the pressure established in the steam chamberor upper compartment 8.

When the steam in the upper compartment 8 is at the desired temperature,the valve 16 is opened and the electric current is supplied to theheating elements 18. The vacuum pump 27 continues to operate with thevalve 26 completely open until the temperature in the lower portion ofthe chamber 2 is at the same temperature as the steam. This will requireabout 7 to 8 minutes. The opening in the valve 26 is now reduced to suchan extent that a uniform temperature will be maintained at the bottomportion of the chamber 2. When the disinfection is terminated, the timedepending on the kind of goods to be treated, the main valve 16 isclosed and the supply of electric current to the elements 18 isterminated. The valve 26 is now opened to render the vacuum pump 27operable to produce a strong negative pressure in the disinfectionchamber 2 to promote drying of the goods therein. As a rule, the lengthof time required for such drying of the goods will not exceed 15minutes.

The consumption of steam for disinfecting goods in accordance with theinvention is rather low. The pressure and also the temperature in thedisinfection chamber 2 is kept fairly constant. The heating elements 18are so dimensioned and constructed that at normal load when electricalenergy is supplied thereto the body of steam maintained in the uppercompartment 8 will remain in the form of saturated steam and excessiveheating effective to change the saturated steam to super heated steamwill be avoided.

When the saturated steam is introduced into the disinfection chamber 2in the manner explained above, it

will require some minutes before the steam reaches the vacuum pump 27and the temperature in the chamber has reached the desired value. Onlythen is the valve 26 adjusted in such a way that there passes throughthe disinfection chamber exactly the required quantity of steam formaintaining the temperature in the disinfecting chamber 2 at a constantvalue. It is to be noted in this connection that a certain amount ofsteam must always pass through the disinfection chamber 2 for otherwisethe temperature in the chamber will drop rapidly.

It is also to be noted that the pressures in the autoclave are adjustedin such a way that the pressure in the disinfection chamber 2 during thedisinfection operation is always kept below the pressure in the uppercompartmentor steam chamber 8.

The shown and described embodiment is to be regarded only as an exampleand the different details of the autoclave may be constructively changedin many ways within the scope of the invention.

What is claimed is:

1. Apparatus comprising (a) structure defining a chamber fordisinfecting articles therein and a housing having first and secondcompartments in communication with one another, said first compartmentbeing at one level and said second compartment being at a higher level,

('b) said first compartment being adapted to hold a body of water, meansfor heating the body of water in said first compartment to generatesaturated steam which passes into said second compartment and forms abody of said saturated steam therein,

(c) an elongated hollow member in said second compartment having aninlet and an outlet and through which said saturated steam generated insaid first compartment is adapted to flow out of physical contact withand enveloped by the body of said saturated steam in said secondcompartment, said elongated hollow member comprising a plurality ofspaced elongated piping sections disposed alongside one another andconnecting ends,

(d) heating means extending lengthwise of said elongated member forheating said saturated steam flowing therethrough to dry the steam, saidheating means comprising a plurality of electrical heating elements,said heating elements extending axially of said piping sections anddisposed in heat exchange relation with said saturated steam adapted toflow therethrough,

(e) an apertured diffuser disposed in the upper part of said chamber,

(f) means for conducting the dry steam from the outlet of said elongatedmember to said apertured diffuser for discharging steam therefrom intosaid chamber,

(g) means in heat exchange relation with said diffuser for heating thesteam introduced therein,

(h) a first evacuating means in communication with said housing abovethe liquid surface level of the body of water in said first compartmentfor producing a first pressure less than atmospheric pressure in saidsecond compartment, and

(i) a second evacuating means in communication with the bottom part ofsaid chamber for withdrawing vaporous fluid therefrom by producing apressure therein which is less than the first pressure in said secondcompartment.

2. Apparatus as set forth in claim 1 in which said structure definingsaid chamber and said first and second compartments of said housingincludes means to position said second compartment in heat exchangerelation with the top of said chamber and said first compartment in heatexchange relation with other parts of said chamber below the topthereof.

a 3. Apparatus as set forth in claim 2 in which said first compartmentof said housing is disposed about said chamber and said secondcompartment of said housing overlies said chamber.

4. Apparatus as set forth in claim 1 in which said means for heatingsaid saturated steam introduced into said apertured diffuser comprisesconduit means for conducting said saturated steam from said firstcompartment to said second compartment, said last-mentioned conduitmeans including a portion for flowing said saturated steam in heatexchange relation and out of physical contact with dry steam introducedinto said diffuser for discharge therefrom into said chamber.

,5. Apparatus as set forth in claim 1 which includes means forregulating the rate at which dry steam flows from the outlet of saidelongated hollow member to said apertured diffuser, said regulatingmeans having a part which is enveloped by the body of said saturatedsteam in said second compartment and formed with a passage for flowingdry steam therethrough.

6. Apparatus as set forth in claim 5 in which said regulating meansincludes a manually operable control member accessible outside saidhousing.

7. A method of disinfecting articles in a space which comprises thesteps of (a) maintaining a body of water in a first place, 7

(b) heating the water in the first place to generate saturated steam,

(c) flowing the saturated steam from the first place to a second placeto provide a body of the saturated steam in the second place,

((1) flowing the saturated steam through an elongated path of flow whichhas an inlet and outlet and is out of physical contact with andenveloped by the saturated steam in the second place,

(e) generating heat electrically lengthwise of said elongated path offlow at axially extending regions thereof which are distributed alongsaid path of flow between the inlet and outlet, such heating beingeflecti ve to heat the saturated steam while flowing through saidelongated path of flow to dry the steam,

(f) flowing the dry steam from the outlet of said elongated path of flowinto a dispersing zone at the upper part of the space and dispersing thesteam into the space at such zone,

(g) heating said dispersing zone at a region in heat exchange relationwith the dry steam introduced therein,

(h) evacuating steam in a first fluid evacuating path of flow from thefirst and second places at a first region above the liquid surface levelof the body of water in the first place when the latter is heated togenerate saturated steam so as to reduce the steam pressure in the firstand second places to a first pressure less than atmospheric pressure,

(i) evacuating air in a second fluid evacuating path of flow from asecond region at the bottom part of the space to reduce the pressuretherein to a second pressure which is less than the first pressure ofthe steam in the first and second places,

(j) heating and flowing saturated steam through said elongated path offlolw and flowing the dry steam therefrom at a first rate to saiddispersing zone when the saturated steam in said first and second placesis at the first pressure and hence at a first temperature,

(k) evacuating steam in the second fluid evacuating path of flow fromthe second region at the bottom part of said space until the temperaturein the bottom part of said space reaches the temperature of the steam,

(l) adjusting the rate at which steam flows from said elongated path offlow to said dispersing zone and is evacuated in the second fluidevacuating path of flow from the second region at the bottom part ofsaid space to maintain the steam in the bottom part of said space at asubstantially uniform temperature to disinfect the articles therein,and, When disinfection of the articles in said space has been completed,

(m) stopping the flow of dry steam from said elongated path of flow tosaid dispersing zone and terminating the heating of saturated steam insaid elongated path of flow, and

(n) evacuating vaporous fluid in the second fluid evacuating path offlow from the second region at the bottom part of said space to promotedrying of the disinfected articles therein.

8. The improvement set forth in claim 7 which further comprises thesteps of flowing a first portion of the saturated steam from the firstplace to the second place in one path of flow and flowing a secondportion of the saturated steam from the first place to the region ofsaid dispersing zone and from the latter to the second place in anotherpath of flow to heat the last-mentioned region, the saturated steampassing through said region in said other path of flow flowing in heatexchange relation and out of physical contact with dry steam at saiddispersing OTHER REFERENCES Peacock et al., J. Pharm. PharmacoL,December 1958,

35 pts. I and II, pp. 47T-59T, Dec. 21, 1956.

JAMES H. TAYMAN, Primary Examiner.

US. Cl. X.R.

